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Blood Clot Prevention: Injection

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Your doctor has prescribed shots (injectable medicine) to prevent or treat blood clots. This medicine is an anticoagulant (an-tihko-AG-you-lent). Sometimes it is referred to as a blood thinner. Along with the anticoagulant medicine, your doctor may prescribe other methods to prevent blood clots. These may include wearing support stockings, doing ankle pumping exercises, getting out of bed the day after surgery, and going to physical therapy. Any or all of these may help to prevent blood clots.

Some common medicines in anticoagulant shots are Lovenox®, Fragmin®, and Arixtra® or heparin. Your doctor will choose the medicine he or she feels is best for you. Some patients may need to take these shots for only a few days until their oral anticoagulant (warfarin or Coumadin®) has time to be effective. Your doctor will tell you how long you need to take your shots.

Taking your medicine

It is very important to follow the instructions for your anticoagulant shot. You should take your shots at the same times every day. Before you start using an injectable anticoagulant, you or a family member will receive special training to learn how to give a shot. If your doctor has also ordered an oral anticoagulant like Coumadin® or warfarin, you must have regular blood tests to see if your dose needs to be adjusted. If the dose of your oral anticoagulant needs to be changed, your doctor will tell you the new dosage to take.

The blood tests will also help your doctor to determine how long you will need to continue taking shots. It is very important that you keep all your appointments for blood tests and follow-up visits with your doctor.  

If you miss a dose

Follow the guidelines below if you miss a dose of your shot.


Call your doctor if you miss a dose of Lovenox®.

Fragmin®, Arixtra®

If you miss a dose of Fragmin® or Arixtra®, take your usual dose as soon as you remember. If you don’t remember until the next day, do not take a double dose. Take your usual dose, and call your doctor.


You will be able to do most of your normal activities while taking this medicine. You need to follow some precautions.

  • If possible, use an electric shaver instead of a blade razor when you shave.
  • Do not engage in contact sports.
  • Do not drink alcohol while taking anticoagulants.
  • Anticoagulants may be dangerous in pregnancy. Call your doctor immediately if you are pregnant or think you may be pregnant. If you plan to become pregnant, discuss this with your doctor or health care provider first.

Be careful about medicines

  • Be sure to store all medicines, including your syringes, according to package instructions.
  • Tell all of your doctors and dentists at all of your appointments that you are taking an anticoagulant.
  • Make sure to review your medicine list with your doctor or health care provider when you start an anticoagulant. Some medicines may keep your anticoagulant from working well.
  • Do not take any aspirin or aspirin products unless your doctor tells you that you may.
  • Do not take any over-the-counter medicines until you check with your doctor or health care provider. This includes over-the-counter cold and pain medicines, herbal products, vitamins, and supplements.
  • Think about getting a medical alert bracelet that says you are taking an anticoagulant.
  • Carry a card in your purse or wallet that lists the medicines you take. Be sure to change the card when you stop taking a medicine or get a new one.

When to call the doctor

If you have any of the following, call your doctor or anticoagulation provider:

  • Bleeding gums or nose that does not stop within a couple of minutes
  • A wound that does not stop bleeding after pressure is applied
  • Blood in your urine or stool
  • Stools that are black or look like tar
  • Vomiting or coughing up blood
  • Bruises that appear for no reason, get larger or more painful, or are sudden or severe
  • Falling and hitting your head
  • Pain, swelling, redness, or warmth in your legs or arms
  • Shortness of breath
  • Chest pain or rapid heart beat
  • Feeling faint or weak

How to give yourself a shot

If your doctor prescribes Fragmin®, Lovenox®, or Arixtra® for you, you will receive this medicine in a prefilled syringe. Before giving the shot, make sure that you have:

  • Prefilled syringe (Figure 1)
  • Alcohol swab or a cotton ball moistened with rubbing alcohol
  • Hard plastic or metal container with a screw-on or tight lid. You will use this to throw away used syringes. Be sure to choose a container that the needle can’t break through. You can use the red “sharps” container if there was one in your injection kit.

Step-by-step guide to give yourself a shot

  1. Clean the tabletop or other area where you will have supplies for your shot.
  2. Wash and dry your hands well.
  3. Choose a place on your abdomen or your thigh for the shot. The place for the injection is called a site (see Figure 2 below for injection sites). The sites may vary depending on the medicine. Ask your doctor or nurse if you are not sure where to give the shot. If you have had surgery, avoid the areas near your incision. Try to use a different site for every shot. If you are giving the shot in your abdomen, leave at least 2 inches between the injection site and your belly button.
  4. Clean the site well with an alcohol pad or a cotton ball soaked in rubbing alcohol. Allow the site to dry.
  5. Remove the cap from the syringe. Pull the cap straight off to keep the needle from bending.
  6. The syringe may contain more than the amount of medicine prescribed. If so, push the plunger until the correct amount of medicine remains in the syringe. Do not expel the small air bubble inside the syringe. The bubble helps push the medicine through the syringe.
  7. Hold the syringe like a pencil in one hand. With the other hand, gently pinch a soft fold of skin where you will give the injection. You must give the injection in the fatty tissue under your skin.
  8. Insert the full length of the needle into the fold of skin at a 45º to 90º angle (see Figure 3). If you are unsure of the proper angle, ask your doctor or nurse. Slowly push the plunger with your thumb into the syringe until all of the medicine is out of the syringe.
  9. Pull the needle straight out of your skin and release the skin fold. If you bleed after removing the needle, place a cotton ball over the skin right away. Press gently on the cotton ball until the bleeding has stopped.
  10. Do not rub the site after you give the injection. If you feel immediate irritation at the injection site, you may want to apply a cool compress.
  11. Throw away the syringe at once in the hard plastic or metal container. Store the container in a safe place away from children. Before disposing of the container in the trash, check your town’s guidelines for syringe disposal.
  12. It is important to watch the previous injection sites for redness, pain, warmth, puffiness, discoloration, oozing, or excessive bruising. All of these may be signs of an infection or skin reaction. Report these problems to your health care professional.
  13. Keep track of your injection sites in a notebook or on an injection diagramlike the one on the next page

Daily log

When you give yourself a shot, look at the diagram (figure 2) and find the letter that is closest to the site where you put the needle in.

Find that letter on the chart to the right and write today’s date in the box.

This will help you keep from using the same sites too often.